a. Background of the Invention
The present invention relates generally to methods and apparatus for repairing pipelines and similar conduits, and, more particularly to a vehicle for delivering expandable patch for internal repair of a pipeline or other conduit.
b. Related Art
Pipelines and similar conduits often require repair, due to erosion, fracturing, corrosion and similar damage. Examples of such conduits include water lines, gas lines, and sewer lines, and these and all similar conduits are included in the terms xe2x80x9cpipexe2x80x9d, xe2x80x9cpipelinexe2x80x9d and xe2x80x9cconduitxe2x80x9d as used herein. Typically (although not always) the pipelines in which the apparatus of the present invention will be used will have a comparatively large diameter (e.g., on the order of 24-60 inches, or larger).
It is usually preferable, especially from an economic standpoint, to repair a damaged pipeline from inside, if this is at all possible. One approach which has been developed for this purpose, and which has been used with considerable success, employs an annular, expandable patch which is forced against the inside of the pipeline so as to form an internal sleeve which covers the damaged area. The internal patch typically is formed of a resin material which is soft and yieldable when it is first expanded against the inside of a pipe, and then subsequently hardens to a tough, rigid condition. One example of an internally expanded patch is the fiber-resin patch that is shown in U.S. Pat. No. 5,322,653 to Mueller.
Although patches of this type have proven successful in and of themselves, a perennial problem has existed as to how to transport the patch through the inside of the pipeline and into position in an efficient and reliable manner. Varieties of transport devices have been used in the prior art and have generally proven less than satisfactory. At one end of the spectrum, there has been the approach of simply xe2x80x9cdraggingxe2x80x9d the patch through the pipeline on some form of plug or body, but this is not a reliable method and can result in excessive damage to the patch; in some instances, an umbrella-shaped shield has been installed in an effort to protect the patch from abrasion as it is being pulled through the pipeline, but again, this has been less than satisfactory, especially in the case of comparably large diameter pipelines where the weight of the assembly, and therefore the friction which it generates, is greatly increased.
A number of wheeled vehicles have also been employed or proposed for carrying the patch into place, but these have generally exhibited drawbacks of their own. The most common form, of vehicle resembles a wheeled xe2x80x9csaw horsexe2x80x9d which supports a cylindrical sleeve and bladder for expanding the annular patch against the inside of a pipe. Although this type of vehicle has the advantage of being simple, it has the maddening tendency to tip over while being pulled through the pipeline, so that the entire assembly must be withdrawn and reassembled for another try. In other instances, wheels have been temporarily mounted directly to the cylindrical support structure, but in many instances this has led to an excessively complex, expensive and cumbersome transport vehicle. Moreover, due to irregularities in the walls of the pipelines (which are often formed of concrete and which may be eroded or worn), and also due to the practical difficulties of trying to maintain the wheels in precise alignment when working in a harsh field environment, prior wheeled transport devices have had a strong tendency to twist or xe2x80x9cwalkxe2x80x9d up the cylindrical walls of the pipeline and also tend to work against each other and bind up; this makes transporting of the patch very difficult and sometimes causes the tow cable and compressed air lines (the latter being used to inflate the bladder) to become twisted.
Accordingly, there exists a need for a transport vehicle for delivering and positioning an expandable, internal pipeline patch that is efficient and reliable in use. Furthermore, there exists a need for such a transport vehicle having an economical and durable form of construction. Still further, there exists a need for such a vehicle that can be pulled through pipelines and other cylindrical conduits with little resistance and without twisting or binding inside the pipeline. Still further, there exists a need for such a vehicle that allows the annular patch to be quickly and easily installed over the cylindrical support and bladder on which the patch is carried and subsequently expanded.
The present invention has solved the problems cited above, and is a tubular transport vehicle having of pivoting wheel assemblies for maintaining the assembly and the annular patch in an upright position as this is transported longitudinally through a cylindrical pipeline.
Broadly, the transport vehicle comprises a cylindrical support structure having a plurality of pivoting wheel assemblies mounted to its forward and rearward ends so as to extend normal to the curved inner surface of the pipeline.
The pivoting wheels may comprise roller wheels that are mounted on caster pivots so as to extend radially from the cylindrical support structure. A ballast member may be mounted to the bottom portion of the cylindrical support member for cooperating with the pivoting wheel assemblies to keep the vehicle upright as it moves longitudinally through the pipeline. The ballast member may comprise at least one weight member that is mounted to an inner surface of the cylindrical support structure.
The vehicle may further comprise an annular bladder for forcing the annular patch against an inside surface of the pipeline in response to inflation of the bladder. The wheel assemblies may be detachably mounted to the cylindrical support structure, so that the wheel assemblies can be detached so as to allow the annular patch to be slipped over the inflatable bladder without having to clear the roller wheels and caster pivots of the wheel assemblies. Alternatively, the wheel assemblies may be inwardly pivotable to provide clearance for the patch to be slipped over the support and bladder.
In a preferred embodiment, the cylindrical support structure is a hollow tubular support, and the pivotable wheel assemblies are mounted thereto at angularly spaced positions with the ballast member being mounted to a bottom portion of the cylindrical support at a position generally between the pivoting wheel assembles.
The detachable wheel assemblies may be provided with clamp portions for selectively mounting the assemblies to the forward and rearward lips of the cylindrical support structure. In the inwardly retractable wheel assemblies, there may be inner and outer support members that are joined by a transverse hinge portion, with the inner support member being permanently mounted to the cylindrical support structure. The support members are locked in the outwardly deployed position by a bolt member which passes through coaxial sleeves mounted on the support members; the locking bolt is configured for being selectively withdrawn from the sleeve portions so as to permit the support member carrying the wheel and caster pivot to be pivoted inwardly about the hinge portion in order to provide clearance for the patch to be slipped over the cylindrical support and bladder.
A compressed air fitting may be provided for supplying air pressure for inflating the annular bladder so as to force the patch against the inside surface of the pipeline.
These and other features of the present invention will be apparent from a reading of the following detailed description with reference to the associated figures.